aussievintage Posted August 20, 2021 Posted August 20, 2021 The big old hysteresis motor on my rek-0-kut started playing at about 2/3 speed until it warmed up, after which it worked absolutely normally. Just soliciting opinions, but I am thinking there is a centrifugal switch in there somewhere to switch in the second winding after it get's up to speed, and it is a bit sticky in the colder weather?
cafe latte Posted August 21, 2021 Posted August 21, 2021 On 20/08/2021 at 10:43 AM, aussievintage said: The big old hysteresis motor on my rek-0-kut started playing at about 2/3 speed until it warmed up, after which it worked absolutely normally. Just soliciting opinions, but I am thinking there is a centrifugal switch in there somewhere to switch in the second winding after it get's up to speed, and it is a bit sticky in the colder weather? Have you serviced the motor? I recently serviced a 301 motor for someone and one bearing was really stiff with gummed old oil. After the service I though it was broken as I could not hear it or see it spinning as it was so smooth, then I picked it up and felt the spindle spinning. Massive difference.. I have not seen rec-o-Kut motor, but most are 4 long bolts and motor comes apart after removing the spindle. Chris 1
t_mike Posted August 22, 2021 Posted August 22, 2021 I second what Chris said, but you could also be on to something with the centrifugal switch idea. In that case, it probably needs the mechanical side of it cleaned and relubed like the motor.
Monkeyboi Posted August 22, 2021 Posted August 22, 2021 I agree with @cafe latte My first approach would be to check that there isn't something as simple as a wiring / switch fault but from your description I'd suspect the bearings in the motor are dry. If I'm not mistaken, many T/T motors of this era used sintered bronze bearings that are known as self lubricating. The truth is they aren't self lubricating from the POV they aren't completely maintenance free. These sintered bronze bearings are impregnated with an oil at manufacture. Yes, you read that correctly. The material is actually porous. In the factory prior to the assembly of the motor, the bushings are oil impregnated by heating them and placing the bushings fully submerged in the lubricating oil and subject to a vacuum. This draws any air out of the material and replaces it with the lubricating oil. Unfortunately over time that lubricant eventually evaporates and what remains is a sticky and gummy mess. As you've discovered, running the motor for a short time tends to soften this up and it then runs at the correct speed. An Aussie Queenslander David Tipton has a YouTube channel mainly accented towards vintage tube radio restoration but he occasionally repairs and restores old turntables. You might find this video interesting - Skip to the 20:00 minute mark for his method of dealing with the dried out bearings issue. Cheers, Alan R.
aussievintage Posted August 22, 2021 Author Posted August 22, 2021 3 hours ago, cafe latte said: Have you serviced the motor? I recently serviced a 301 motor for someone and one bearing was really stiff with gummed old oil. After the service I though it was broken as I could not hear it or see it spinning as it was so smooth, then I picked it up and felt the spindle spinning. Massive difference.. I have not seen rec-o-Kut motor, but most are 4 long bolts and motor comes apart after removing the spindle. Chris I haven't done a full strip down. The reason I don't think it's just sticky, is that it runs smoothly and constantly at the lower speed. It does not slowly speed up as it warms up.
aussievintage Posted August 22, 2021 Author Posted August 22, 2021 2 hours ago, Monkeyboi said: I agree with @cafe latte My first approach would be to check that there isn't something as simple as a wiring / switch fault but from your description I'd suspect the bearings in the motor are dry. No way. They are swimming in oil The motor has oil pipes which feed oil to the bearings and I put plenty in when I got it. I read that the oil goes to a felt storage (ring?) that keeps the bearings fed with oil. 1
aussievintage Posted August 22, 2021 Author Posted August 22, 2021 2 hours ago, t_mike said: I second what Chris said, but you could also be on to something with the centrifugal switch idea. In that case, it probably needs the mechanical side of it cleaned and relubed like the motor. Yes, and the switch will probably be inside the motor I suspect, so I will have to pull it apart as Chris suggested. 1
cafe latte Posted August 22, 2021 Posted August 22, 2021 2 hours ago, Monkeyboi said: I agree with @cafe latte My first approach would be to check that there isn't something as simple as a wiring / switch fault but from your description I'd suspect the bearings in the motor are dry. If I'm not mistaken, many T/T motors of this era used sintered bronze bearings that are known as self lubricating. The truth is they aren't self lubricating from the POV they aren't completely maintenance free. These sintered bronze bearings are impregnated with an oil at manufacture. Yes, you read that correctly. The material is actually porous. In the factory prior to the assembly of the motor, the bushings are oil impregnated by heating them and placing the bushings fully submerged in the lubricating oil and subject to a vacuum. This draws any air out of the material and replaces it with the lubricating oil. Unfortunately over time that lubricant eventually evaporates and what remains is a sticky and gummy mess. As you've discovered, running the motor for a short time tends to soften this up and it then runs at the correct speed. An Aussie Queenslander David Tipton has a YouTube channel mainly accented towards vintage tube radio restoration but he occasionally repairs and restores old turntables. You might find this video interesting - Skip to the 20:00 minute mark for his method of dealing with the dried out bearings issue. Cheers, Alan R. Almost right, you dont put in a vacuum, you just boil in oil and the bearing will start fizzing as the air is driven out of the pores as it expands. Then leave to cool in the oil and oil is drawn in to pores and job is done. Chris 1
cafe latte Posted August 22, 2021 Posted August 22, 2021 34 minutes ago, aussievintage said: No way. They are swimming in oil The motor has oil pipes which feed oil to the bearings and I put plenty in when I got it. I read that the oil goes to a felt storage (ring?) that keeps the bearings fed with oil. The Commonweath has the same oil tubes but you will need to remove the bearings to clean the varnish off. Chris
Monkeyboi Posted August 22, 2021 Posted August 22, 2021 2 minutes ago, cafe latte said: Almost right, you dont put in a vacuum, you just boil in oil and the bearing will start fizzing as the air is driven out of the pores as it expands. Then leave to cool in the oil and oil is drawn in to pores and job is done. Chris Hmmm... boiling in oil at home? Somehow I think I prefer Dave's method. Probably not as dangerous in a domestic situation. However as the motor in question uses a completely different lubrication method (you learn something new every day) the point is now mute. Thanks for the heads up. Cheers, Alan R.
cafe latte Posted August 22, 2021 Posted August 22, 2021 (edited) 4 minutes ago, Monkeyboi said: Hmmm... boiling in oil at home? Somehow I think I prefer Dave's method. Probably not as dangerous in a domestic situation. However as the motor in question uses a completely different lubrication method (you learn something new every day) the point is now mute. Thanks for the heads up. Cheers, Alan R. It is simple, get a pan (not missus fav) and add oil, heat up on stove like you are going to make chips, I use the Barby as it is outside. Drop bearings in and wait till fizzing and wait till the fizzing stops, then turn off heat and leave till cool. This is the only method, heat is needed expand the air and also to melt varnished oil that will be blocking the pores. The turntable in question has sintered bronze bearing with an oil tube (like the Commonwealth) the oil tube helps keep bearings wet with oil, but after all these decades the pores will be blocked a reoil boiling will make a big difference. Chris Edited August 22, 2021 by cafe latte 1 1
aussievintage Posted August 22, 2021 Author Posted August 22, 2021 15 minutes ago, cafe latte said: The Commonweath has the same oil tubes but you will need to remove the bearings to clean the varnish off. Chris Well, I still can't imagine how varnish can induce this two speed behaviour. Doesn't really matter as the motor has to come apart anyway, even if it turns out to be a centrifugal switch that needs cleaning. I will be cleaning everything while it is apart. 1
cafe latte Posted August 22, 2021 Posted August 22, 2021 58 minutes ago, aussievintage said: Well, I still can't imagine how varnish can induce this two speed behaviour. Doesn't really matter as the motor has to come apart anyway, even if it turns out to be a centrifugal switch that needs cleaning. I will be cleaning everything while it is apart. The Commonwealth I recently did the motor on had a varnish ring on the shaft that was acting like a handbrake until warm. Cleaning it off was the only way. Chris 1
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